An increasing number of bogs in production are reaching the stage in which their surface area is reducing and production is becoming difficult as the peat layer becomes thinner. On the other hand, the requirements of environmental permits have become stricter in terms of emissions to watercourses and of dust and noise. Production possibilities are also limited in the neighbourhood of settlements. It is increasingly difficult to obtain permits for new bogs, so that existing bogs, together with their margins should be exploited more fully.
A so-called hydro-peat method, for example, GB 166,576, is known, in which a water jet is used to remove peat from a bog and pump it as a very thin sludge to a drying field, which is usually an area of bog that has been taken out of production. The mass, which is spread on the field as a thin sludge, is allowed to dry for several weeks, after which at least longitudinal slits, preferably in a briquette-sod pattern, are made in the drying paste-like mat, thus forming separate briquettes when the mass dries. Using this technique, it is possible to obtain perhaps only a single harvest in a summer, so that the total production efficiency remains modest.
Finnish patent FI-93855 discloses a peat production method, in which wet peat is removed from a bog and collected to form a stack at a selected point in the peat field, the dried side surface of which is turned to the other side at regular intervals. In this case too, the production remains modest.
The basic problem in peat drying appears to be that drying takes place on a wet surface, which hinders the drying process. The drying that takes place during the day is often lost as a result of night dew. Finnish patent publication 56853 discloses a method, in which peat is lifted mechanically in winter and set as small sods on plastic to dry, allowing the sods to dry even before the bog is able to thaw out.
In the production of horticultural peat too, the aim is to dry the peat before processing it further.